mttlaspia
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Copper Sulfate Production
I set up an electrolytic cell with a copper anode (-) and carbon cathode (+) in a concentrated solution of MgSO4. I'm using DC power source and
running about 8V with 2amps. The reaction seems to work at first, but after a while it forms Cu(OH)2. I don't know if I'm running the cel too long or
what. Does anyone know if there i a formula for how long it will take for a reaction to carry out with any given number of volts/amps?
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Arthur Dent
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Hi!
Perhaps you might want to lower the voltage a bit (5 or 6v), are both of your electrodes releasing gas? If so, your voltage might be too high. Only
the negative electrode should bubble.
Robert
[Edited on 7-1-2011 by Arthur Dent]
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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violet sin
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how well does this method work? I have made a lot of copper hydroxide on purpose, and while experimenting with electrode metals, sizes and
spacing. ( before I found this site). with all the batches of hydroxide, I never got a single copper sulfate grain left at the bottom of any of my
cells. epsom salt, magnesium hydroxide, copper hydroxide, Cu oxides and tap water scum, sure, but not copper sulfate.
I was running a hacked 230W ATX power supply, and switched off between the 5V, 6A and the 12V, 18A hots w/ common ground (eventually stuck w/
12v). though I am sure it was only operating at a fraction of that. any how I tried CU, Ti, Fe, Ta and C electrodes for the cell(s), and milk jugs
cut in half for containers. up to 3 in a series chain. parallel worked less favorably for me.
I was mainly interested in the Cu(OH)2 for decomp to oxide for colored flames in my copper coil alcohol burner i had just made. ( looked awesome
btw) but after I realized that the epsom salt was magnesium sulfate( duh, I know right? ) I tried to intentionally make the copper salt. so if this
works I have a big pile of copper and I love blue, my fave color.
do you think with my current power supply I could do that? or would I need to wire one up tailored to a specific voltage/amperage range like
listed above?
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woelen
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It is obvious that this method does not give CuSO4.
At the anode, there is formation of Cu(2+) ions. At the cathode, hydrogen is formed and hydroxide ions. The reaction at the cathode is:
2H2O + 2e --> 2OH(-) + H2
The H2 escapes as gas, the OH(-) ions mostly will react with Mg(2+) to form sparingly soluble Mg(OH)2 and if this comes in contact with the copper
ions, then insoluble Cu(OH)2 is formed. Your solution will become turbid soon after starting the electrolysis process.
If you really want a good product, then you need dilute H2SO4. At the cathode, H(+) ions are consumed and at the anode, Cu(2+) ions are formed. There
is one complication though. At increasing concentration of Cu(2+) ions, more and more of a side reaction occurs at the cathode, where Cu(2+) will be
converted to Cu-metal.
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elementcollector1
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Or, you could just use two cells for your electrolysis... Copper anode, random cathode, anolyte concentrated epsom salt, catholyte something
conductive.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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woelen
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Two cells does not solve the problem. It is just a series connection of two cells and each of the cells behaves exactly as if they were one cell. The
piece of metal, which connects the two cells acts as anode in the cell, which is connected to the power supply cathode (negative pole) and it acts as
cathode in the cell, which is connected to the power supply anode (positive pole).
A true solution is either a cell with a permeable membrane between anode liquid and cathode liquid, or a solution bridge between two cells. One could
make a cell with dilute H2SO4 and the other with Na2SO4 and have a bridge between the cells with dilute H2SO4 in it. Such a cell would do the job for
quite a long time.
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zed
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Yup. Probably have to use Sulfuric Acid.
I don't do it that way myself, 'cause I have more Copper Sulfate than I will probably ever use.
I just went up to Home Depot, and bought a big jar full of 99.9% Copper Sulfate root killer.
The way I remember it, for 10 to 15 dollars, I got a few pounds.
Comes in handy if you want to do some Copper plating.
[Edited on 12-9-2012 by zed]
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elementcollector1
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woelen: Not a metal bridge. A tissue paper bridge, as to transfer ions and not electrons. Admittedly, if the sulfuric acid produced in the anolyte
gets concentrated enough, this will dissolve away, but I think that with a large enough, etched copper cathode this won't happen (as fast).
This will make copper sulfate from Epsom salt, but not very concentrated and, unless you run the electrolysis for a very long time, not very pure.
Better to just buy it.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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kilowatt
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I've been down that road of electrolysis before and found it much faster and more efficient to start with copper oxide. A solution of hydrochloric
acid and 3% hydrogen peroxide will eat copper at an alarming rate, and you can precipitate copper oxide from that chloride solution. It will dissolve
much more readily in the acid. Even more quickly (if you have the apparatus to scrub the gas) you can just add sulfuric acid right to the chloride
solution and drive off HCl, but you will either have to contend with a little excess sulfuric acid to drive off, or be left with some CuCl2 impurity.
I did something like this (actually with CuCl2 that I had made from the precipitated and filtered oxide) with a very slight excess of sulfuric acid
once and bubbled the HCl into water, eventually obtaining white anhydrous CuSO4 which naturally rehydrated to blue.
[Edited on 25-9-2012 by kilowatt]
The mind cannot decide the truth; it can only find the truth.
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